Impact of a physically based soil water flow and soil-plant interaction representation for modeling large-scale land surface processes

The aim of this paper is to improve our understanding and the representation of hydrological and energetic exchanges between the soil, the vegetation, and the atmosphere at the continental scale. The soil hydrology of the land surface scheme Schématisation des Echanges Hydriques l'Interface entre la Biosphère et l'Atmosphère (SECHIBA) is improved. It is derived from the physically based hydrological model of the Centre for Water Resources Research and is adapted to the representation of soil-plant-atmosphere interactions at large scale and to the coupling with an atmospheric model. In the new model, soil-plant interactions result from root-soil moisture profile interactions, represented on a fine vertical resolution. This allows a better control of land evapotranspiration by soil-vegetation systems. SECHIBA in this new version takes into account a subgrid-scale variability of soil texture. Different possibilities of interactions between soil and vegetation variabilities allow the representation of various soil-plant-atmosphere systems. It is shown that the distribution of vegetation on the soil and the soil texture influence the way in which soil, plants, and atmosphere interact.